Tim Kaine, the Democratic vice-presidential nominee, used a speech Saturday in New Hampshire to lambaste Donald Trump for his continued refusal to release his tax returns, suggesting the Republican presidential nominee was trying to hide a “stingy” history of charitable giving and questioning his commitment to the military.

“He’s bragged about using every trick and artifice he can to pay no taxes,” Kaine, a U.S. senator from Virginia, said of Trump. “We pay taxes to support the military. … If you haven’t been supporting the military during your entire life, don’t tell me you’ll suddenly start if you get to be commander...